here is a nested test
\begin{one}
	[
		optional argument
	]
	% comment here
	[
		\[x^2\] % trailing comment
		another optional argument
	]
	% here
	[
		third optional argument %another 
	]
	% another comment 
	to be nested to be nested
	to be nested to be nested
	to be nested to be nested
\end{one}
